Hey Joe,
set up a coarser grid around the native conditions. I know of one case
where semet crystallized nearly 2 full pH units lower than native. A
colleague made a couple of years ago a reasonable suggestion: don't do
s-met at all, do the crystal screening directly with se-met. Nowadays
certainly affordable.
good luck
Jens
On Tue, 2008-05-27 at 17:11 -0400, Joe Smith wrote:
> Dear all,
> Sorry for an off-topic query.
> I have been unable to crystallize a Se-met containing protein (8 Met
> in 206 amino acids) in the native crystallization condition ( 0.1 M
> Tris pH 8.5, 1.2 M K-Na-tartrate; Theoretical pI of protein is 8.4).
> As expected, solubility of Se-Met containing protein is little less
> than the wild type. Other than seeding, i don't know what else I
> should try for obtaining a Se-met crystal for phasing. Can I mutate
> some of the exposed Met (based on secondary structure prediction and
> homologous structure) to Ala as I feel I don't really need 8 Se for
> phasing 208 aa long polypeptide. I want to know what generally one
> should do when Se-Met containing proteins fail to crystallize.
> Thanks in advance.
> Joe
> PS: Since, protein contains 3 Cys residues.. I am also planning to try
> my luck with heavy atom compounds containing Hg.
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